Method of enhancing the acetate dyeability of vinylidene cyanide interpolymers



METHOD OF ENHANCING THE ACETATE DYE- ABILITY OF VINYLIDENE CYANIDE INTER- POLYMERS George Gateir, Lakewood, and Stephen M. Davis, Elyria, @1110, assignors to The B. F. Goodrich Company, New York, N. Y., a corporation of.New York No Drawing. Application November 30, 1955 Serial No. 550,219

6 Claims. (Cl. 260-785) This invention relates to methods for enhancing the dyeability of certain types of hydrophobic synthetic fibers, and more particularly relates to a pre-dye treatment of vinylidene cyanide interpolymer fibers which employs a particularly desirable catalyst for the hydrolysis reaction of fiber side chain groups.

Vinylidene cyanide fiber-forming interpolymers are described in U. S. Patents Nos. 2,615,865 through 2,615,880, 2,628,954, 2,650,911, 2,654,724, 2,654,728, 2,657,797, 2,716,104 through 2,716,106, and in copending applications, Serial Nos. 402,823, filed January 7, 1954, now Patent No. 2,786,046; 407,595, filed February 1, 1954, and 526,335, filed August 3, 1955. As described therein, synthetic fibers spun from such interpolymers possess unusually high strength and other desirable properties.

To be of value to the trade, however, any synthetic fiber produced must be readily and successfully dyeable, preferably with the dyes and techniques currently in use for standard market fibers. Like many hydrophobic synthetic fibers and filaments, those made from vinylidene cyanide interpolymers have slick, smooth surfaces and are resistant to penetration by ordinary dyestuffs. Further, these polymeric fibers oifer a minimum of points or molecular groups to which dye molecules may become affixed through chemical bonding. Heretofore the dyeing of vinylidene cyanide interpolymer fibers with acetate dyes alone has produced weakly colored fibers lacking in attractiveness and in resistance to laundering.

One approach to the problem, used successfully with fibers made of cyanide containing polymers of the polyacrylonitrile types, has been copolymerization with monomers containing basic groups. This procedure fails with polymers based on vinylidene cyanide,-however, for this monomer, as demonstrated in the art, homopolymerizes under polymerization conditions when basic groups or water are present, even in small amounts.

Another expedient to encourage dye penetration of these synthetic fibers is to open the fiber structure by the action of a swelling agent. Swelling agents are often applied to the fibers before the fibers are treated with the dye, but many of them are added directly to the dye bath and reach the fibers concurrently with the dye. Phenyl phenol, benzoic acid, and monochlorobenzene have been used in pre-dye treatments. Swelling agents useful for incorporation into the dye bath include: aromatic amines such as aniline, p-chlcroaniline, alpha-naphthylamine and m-toluidine, nitroaromatic compounds such as p-nitrotoluene, nitrobenzene, m-dinitrobenzene, and pnitrodiphenyl as well as salicylic acid, chlorosalicylic acid, quinoline, isoquinoline, acetophenone, chloroacetophenone, and benzaldehyde.

It is an object of this invention to provide a process for treating vinylidene cyanide interpolymers to render fibers and films formed therefrom readily dyeable with acetate dyes. Another object is to provide a treating process that will not require the use of high temperatures or potentially toxic concentrations of chemicals to make I nited States Patent vinylidene cyanide interpolymers dyeable with acetate dyes.

Yet another object is to provide textiles made of vinylidene cyanide interpolymer fibers, filaments, yarns and fabrics which are dyeable with standard, commercially available dyes which possess, when so dyed, light, cleaning and laundering fastness comparable to dyed woolen fibers and fabrics, and having at the same time an unimpaired hand or feel.

These and other objects are readily attained by the process of hydrolyzing the vinylidene cyanide interpolymer under acidic conditions before forming fibers and films which are then immersed in the acetate dye bath. The nature andamount of catalyst used and the time and temperature conditions of the process are critical to proper control in order to produce dyed fiber of high quality. By increasing the catalyst concentration, the time, or the temperature, nitrile side groups can be hydrolyzed to amide, amidine, or carboxyl groups, but use of too drastic conditions will destroy polymer linkages thereby decreasing fiber transparency and tenacity, and making the fiber brittle and heat sensitive. If, however, only a partial hydrolysis of the side functional groups to hydrophilic groups is accomplished, the ultimate properties of the fiber will not be seriously altered while acetate dyeing will be measureably improved.

We have discovered that a pre-dye hydrolysis treatment of vinylidene cyanide interpolymers converts a substantial proportion of side groups of the polymer chain into carboxyl or hydroxyl groups and makes the fibers much more readily dyeable with acetate dyes. Another phase of our discovery is that a particular catalyst, mercuric sulfate, leads to outstanding dyeing results when used as the hydrolysis catalyst in the treatment of vinylidene cyanide interpolymers. The depths and fastness of shades obtained on the vinylidene cyanide. interpolymer fibers are comparable to .those obtained when using the same acetate dyes on hydrophilic fibers. I

Any vinylidene cyanide interpolymer may be used. Such, interpolymers contain TillCN groups in their structure and the preferred interpolymers arebicomponent interpolymers in which the vinylidene cyanide residue shown alternates in 1 to 1 molar ratio with the residue of the comonomers. Specific vinylidene cyanide interpolymers which may be used are disclosed in the patents enumerated in the second paragraph hereof, the disclosures of which are incorporated herein by refer ence. The most preferred interpolymer is the l to 1 molar interpolymer of vinylidene cyanide with vinyl acetate.

Although hydrolysis reactions may generally be cat alyzed by either acidic or basic catalysts, it is necessary in hydrolyzing vinylidene cyanide interpolymers that acids be used since such interpolymers are generally somewhat caustic sensitive and the fibers would be degraded by caustic treatment.

Not all acid hydrolysis systems can be used in the'practice of this invention for care must be used to avoid lows better reaction control since the acid in this case is neutralized by ammonia formed as the nitrile groups on the interpolymer are hydrolyzed. Another problem is encountered, however, in finding a solvent for the polymer which will not itself hydrolyze in the presence of hydrochloric acid or other hydrolysis catalyst, and from which satisfactory fibers can be spun. None of the known vinylidene cyanide interpolymer solvents such as acetonitrile or dimethylformamide meet this requirement. The use of a mixture of 95% dimethylformamide and water has been found to result in fiber of good appearance while an even more preferred polymer solvent is 95 percent acetone, 4 percent dimethylformamide and 1 percent sulfuric acid. Since the latter solvent is composed mainly of low cost acetone, it is a very economical solvent to use. It has been found to give better control of coagulation in the fiber spinning step and better transparency in the final fiber. Tensile and elongation tests run on the modified interpolymer fibers, indicate that the fibers are degraded too much to make hydrochloric acid catalyzed hydrolysis desirable.

We have discovered that the use of mercuric sulfate formed in situ as the hydrolysis catalyst with the interpolymer dissolved in 95 percent acetone, 4 percent dimethylformamide and 1 percent sulfuric acid produces modified vinylidene cyanide: vinyl acetate copolymer fibers which dye readily in acetate dyes and retain the physical properties of an acceptable fiber. The order of addition of the catalyst ingredients has been found to be important. Mercuric acetate is added first and stirred until its distribution is homogeneous; then the stoichiometric amount of sulfuric acid is added to form mercuric sulfate. The necessary amount of mercuric sulfate was found to be from 0.75% to 1.5%, based on the weight of the interpolymer.

Advantages which may be cited for the synthetic materials dyed by the process of this invention include complete penetration of the dye into the fiber and no change in hand or feel of the fabric.

The examples given below are intended only to illustrate the advantages of this invention and are not to be construed as a limitation upon the scope thereof, for there are, of course, numerous possible variations and modifications that will be apparent to those skilled in the art. In the examples, all parts are parts by weight.

Example 1 Following the teaching of U. S. Patent 2,615,866, a supply of vinylidene cyanide: vinyl acetate copolymer was prepared in the form of a dry powder. Ten percent solutions of the copolymer were made in (l) acetonitrile, (2) 95 percent dimethylformamide and 5 percent water, and (3) 94 percent acetone, 5 percent dimethylformamide and 1 percent sulfuric acid. All solutions were colorless and gave clear flexible films when cast on a hot plate so that the solvent would evaporate. A study of solution (3) showed that when the level of sulfuric acid was increased and a film cast, that the dope solution became increasingly discolored and the films increasingly brittle.

Example ll Solutions similar to those of Example I were prepared in triplicate, using 20 percent strength of copolymer. One of each type of solution was reserved for a control. To the other two of each type of solution one percent mercuric acetate, based on the polymer content was added and stirred about minutes until it was homogeneously distributed; then a stoichiometric amount of sulfuric acid based on the amount of mercuric acetate was added. The second set of each solution of this example was set aside for Example III, the third set was placed in a 60 C. oven for three hours. During this time the solutions were shaken every half hour. Films were cast by pouring the warmed solutions in thin layers on hot plates at 50-60 C. and allowing the solvent to evaporate.

The clear films were placed in dye baths containing 5 percent on weight of film of Eastman Blue. BLT, an acetate type dye stuff, at a bath liquor to film ratio of 40 to l and were held at boil for one hour. After dyeing the films were rinsed in cold water. All of the films from hydrolyzed polymer were satisfactorily dyed. Films cast from the control solutions were not dyed at all.

Example III The remaining portions of the solutions prepared in Example II were stirred for 3 hours at 60-70 C., then extruded through a multi-hole spinneret to form fibers which were collected in a water bath, dried, and placed in dye baths containing 5 percent on weight of fiber of Eastman Blue BLT dye stuff and a bath liquor to fiber ratio of 40 to l where they were held at boil for one hour. The dyed fibers were thoroughly rinsed and evaluated. All had accepted dye and substantially retained their original physical properties.

The actual hydrolysis catalyst used in Examples II and III was mercuric sulfate formed in situ. It is believed that nitrile groups along the copolymer chain were hydrolyzed to carboxyl groups and acetate side groups were hydrolyzed to free alcohol groups. Such groups tend to increase the hydrophilicity of the fiber and increase diffusion and penetration of dye into the fiber or film. Repeat runs increasing the amount of sulfuric acid inthe acetone, dimethylforinamide, sulfuric acid solution showed that a higher level of sulfuric acid formed a better polymer solvent, but led to discoloration of the dope and brittle films.

Acetonitrile was found to be an unsatisfactory solvent for fiber dyeing. It hydrolyzes under the influence of the catalyst causing cloudy dope and bubbles in the spinning solution. Films cast from acetonitrile (Example II) did dye very well, however.

The DMF-water solvent produced a fiber which accepted acetate dye satisfactorily. The fiber retained its transparency and showed no brittleness. The DMF- water films also dyed satisfactorily, remained transparent, and were not embrittled.

The acetone-DMF-sulfuric acid solvent was the most effective of all those tried in this example. it is economical, and its use results in slower coagulation of fiber in the spinning bath as well as in fibers of improved transparency. The amount of sulfuric acid in the solvent was shown to be critical. The polymer dissolved better when more than one percent of sulfuric acid was present, but such solutions were discolored and produced brittle films and fibers.

Control runs of unhydrolyzed copolymer from all the solvents did not accept any dye at all indicating that the mercuric sulfate catalyzed hydrolysis had modified the vinylidene cyanidezvinyl acetate copolymer sufiiciently go make it accept acetate dyeing in either film or fiber orm.

The foregoing examples are merely illustrative, and not limit ng, of the scope of this invention. Variations and modifications of the invention will be apparent to those skilled in the art. The invention is intended to be limited only by the scope and spirit of the appended claims.

We claim:

1. The process for enhancing the acetate dyeability of 50 mol percent vinylidene cyanide interpolymers with olefinically unsaturated monomers which comprises hydrolyzing such interpolymers in a solvent solution selected from the group consisting of (1) dirnethylformamide and water, and (2) acetone dimethylformamide (4% and sulfuric acid (1%) using mercuric sulfate as an hydrolysis catalyst for a time and at a temperature sufficient for the mercuric sulfate to catalyze the hydrolysis of a significant proportion of the side chain groups in the vinylidene cyanide interpolymer structure.

2. The process for enhancing the acetate dyeability of 50 mol percent vinylidene cyanide interpolymers with olefinically unsaturated monomers which comprises hydrolyzing such interpolymers in a solvent solution selected from the group consisting of 1) dimethylformamide and Water, and (2) acetone (95%), dimethylformamide (4%), and sulfuric acid (1%) with 0.75% to 1.5 on Weight of interpolymer of mercuric sulfate as an hydrolysis catalyst for a time and at a temperature sufficient for the mercuric sulfate to catalyze the hydrolysis of a significant proportion of the side chain groups in the vinylidene cyanide interpolymer structure.

3. The process for enhancing the acetate dyeability of 50 mol percent vinylidene cyanide interpolymers with olefinically unsaturated monomers which comprises hydrolyzing such interpolymers in a solvent solution selected from the group consisting of 1) dimethylformamide and water, and (2) acetone (95 dimethylformamide (4%), and sulfuric acid (1%) using 1% on weight of interpolymer of mercuric sulfate as an hydrolysis catalyst for a time and at a temperature sufiicient for the mercuric sulfate to catalyze the hydrolysis of a significant proportion of the side chain groups in the vinylidene cyanide interpolymer structure.

4. The process for enhancing the acetate dyeability of 50 mol percent vinylidene cyanide interpolymers with olefinically unsaturated monomers which comprises hydrolyzing such interpolymers in a solvent solution selected from the group consisting of (1) dimethylformamide and water, and (2) acetone (95%), dimethylformamide (4%), and sulfuric acid (1%) using a catalyst comprising 0.75% to 1.5% on weight of interpolymer of mercuric sulfate formed in situ by reaction of mercuric acetate and sulfuric acid, for a time and at a temperature sufficient for the mercuric sulfate to catalyze the hydrolysis of a significant proportion of the side chain groups in the vinylidene cyanide interpolymer structure.

5. The process for enhancing the acetate dyeability of :50 mol percent vinylidene cyanidezvinyl acetate copolymer which comprises hydrolyzing such copolymer in a solvent solution selected from the group consisting of (1) dimethylformamide and water, and (2) acetone dimethylformamide (4%), and sulfuric acid (1%) using mercuric sulfate as an hydrolysis catalyst for a time and at a temperature sufficient for the mercuric sulfate to catalyze the hydrolysis of a significant proportion of the side chain groups in the vinylidene cyanidezvinyl acetate copolymer structure.

6. The process for enhancing the acetate dyeability of 50:50 mol percent vinylidene cyanidezvinyl acetate copolymer which comprises hydrolyzing such copolymer in a solution selected from the group consisting of (1) dimethylformamide and water, and (2) acetone (95 dimethylformamide (4%) and sulfuric acid (1%), using as an hydrolysis catalyst 0.75% to 1.5% on weight of copolymer of mercuric sulfate formed in situ by reaction of mercuric acetate and sulfuric acid for a time and at a temperature sufficient for the mercuric sulfate to catalyze the hydrolysis of a significant proportion of the side chain groups in the vinylidene cyanidezvinyl acetate copolymer structure.

References Cited in the file of this patent UNITED STATES PATENTS 2,579,061 Woodward Dec. 19, 1951 

1. THE PROCESS FOR ENHANCING THE ACETATE DYEABILITY OF 50 MOL PERCENT VINYLIDENE CYANIDE INTERPOLYMERS WITH OLEFINICALLY UNSATURATED MONONERS WHICH COMPRISES HYDROLYZING SUCH INTERPOLYMERS IN A SOLVENT SOLUTION SELECTED FROM THE GROUP CONSISTING OF (1) DIMETHYLFORMAMIDE AND WATER, AND (2) ACETONE (95%), DIMETHYLFORMAMIDE (4%), AND SULFURIC ACID (1%) USING MERCURIC SULFATE AS AN HYDROLYSIS CATALYST FOR A TIME AND AT A TEMPERATURE SUFFICIENT FOR THE MERCURIC SULFATE TO CATALYZE THE HYDROLYSIS OF A SIGNIFICANT PROPORTION OF THE SIDE CHAIN GROUPS IN THE VINYLIDENE CYANIDE INTERPOLYMER STRUCTURE. 